From: "Björn Töpel" <bjorn.topel@intel.com>
To: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Björn Töpel" <bjorn.topel@gmail.com>,
ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
bpf@vger.kernel.org
Cc: kafai@fb.com, songliubraving@fb.com, yhs@fb.com,
andrii@kernel.org, john.fastabend@gmail.com, hawk@kernel.org,
kuba@kernel.org, magnus.karlsson@intel.com,
maciej.fijalkowski@intel.com
Subject: Re: [PATCH bpf-next] bpf, xdp: add bpf_redirect{,_map}() leaf node detection and optimization
Date: Wed, 2 Dec 2020 08:55:56 +0100 [thread overview]
Message-ID: <f7480e4a-26f5-b3fa-69b9-3a80e4cc362d@intel.com> (raw)
In-Reply-To: <87y2ihyzhp.fsf@toke.dk>
On 2020-12-01 22:42, Toke Høiland-Jørgensen wrote:
> Björn Töpel <bjorn.topel@gmail.com> writes:
>
[...]
>>
>> Performance up ~5% Mpps for the xdp_redirect_map and xdpsock samples,
>> and ~3% for bpf_redirect() programs.
>
> Neat! Got actual numbers? :)
>
+~1 Mpps for AF_XDP, and +~3 Mpps for a naive (non-swapping) redirect.
[...]
>
> This seems like an awful lot of copy-paste code reuse. Why not keep the
> __xdp_map_lookup_elem() (and flags handling) in bpf_xdp_redirect_map()
> and call this function after that lookup (using ri->tgt_value since
> you're passing in ri anyway)? Similarly, __bpf_tx_xdp_map() already does
> the disambiguation on map type for enqueue that you are duplicating here.
>
> I realise there may be some performance benefit to the way this is
> structured (assuming the compiler is not smart enough to optimise the
> code into basically the same thing as this), but at the very least I'd
> like to see the benefit quantified before accepting this level of code
> duplication :)
>
Good points; I'll need to take this to the drawing board again. Please
refer to Alexei's reply.
Thanks for taking a look!
Björn
next prev parent reply other threads:[~2020-12-02 7:57 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-01 17:23 [PATCH bpf-next] bpf, xdp: add bpf_redirect{,_map}() leaf node detection and optimization Björn Töpel
2020-12-01 21:42 ` Toke Høiland-Jørgensen
2020-12-02 7:55 ` Björn Töpel [this message]
2020-12-02 4:46 ` Alexei Starovoitov
2020-12-02 8:01 ` Björn Töpel
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